Operations in littoral waters present numerous challenges for modern navies, challenges that are especially acute in the waters of the Baltic Sea and around Northern Europe. Russia's increasing menace above, on, and under the waves—combined with its deployment of new and upgraded maritime capabilities and considerable commercial and civilian activity in the region—calls for enhanced vigilance from the United States and its allies and partners. This report explores the changing nature of maritime domain awareness (MDA) in the Baltic Sea and Norwegian Sea and offers recommendations for establishing effective MDA in these basins. Ultimately, the challenges in these regions necessitate multilateral, networked, and cost-effective solutions that leverage advancing technology and enhanced operational concepts.